A whole range of solutions have already been proposed for the problem of armor-plating bodywork, however they all suffer from a major drawback they make use of materials which are heavy, thick, and usually made of metal, which often make this type of operation impossible, for example, on civilian vehicles whose structure and power are not up to the weight of such armor plating.
When armor-piercing bullets are used (i.e. bullets including an extremely sharp tungsten core covered in a lead alloy which is in turn covered in brass), the thickness of material that would be required is prohibitive.
In order to stop an armor-piercing projectile, it is already known that sintered industrial ceramics may be used, which ceramics may be based on alumina or on silica, serving to break the core such that immediately after penetrating it is no longer pointed but becomes blunted or may even disintegrate into several pieces. Such a core can then be stopped by a layer of composite armor plating of the Antigun (registered trademark) type or by any other light armor plating.
However, the problem which remains and which is solved by the present invention is the problem of cohesion in composite panels comprising the ceramic and either stainless steel, or aluminum, or else a panel of the Antigun type.
Glues are known which serve to hold together various layers with adequate adhesion. However, in the event of a violent shock such as a bullet impact, it turns out that the various layers come unstuck from one another. The shockwave produced in the event of a projectile impact may reach a speed of about 9,000 meters per second (m/sec), whereas the speed of the projectile is only 800 m/sec. This produces a corresponding change in volume which, independently of any mechanical effect shatters the layer of adhesive if it is hard, thereby deliminating or clearing apart the layers, and possibly causing the outer layer to fall off, if made of ceramic tiles. As a result, after impact, the ceramic tiles adjacent to the tile which receives the projectile either fall off or else are cracked, which leads to the use of an external retaining or protective layer so that the tiles are held in place after the impact of a projectile solely by the outer retaining layer.
French patent No. FR-A-2 565 162 describes a polyurethane which is laminateable at low temperature and which is intended to stick together two transparent layers such as glass and polycarbonate.
German patent No. DE-A-2 344 277 relates to a bullet-proof jacket comprising multi-layer plates constituted by a metal layer and a layer of inorganic material which are interconnected by a layer of elastomer such as rubber, polyurethane, PVC, etc. However, the purpose of this layer is solely to distribute energy and not to stick the layers together with the elastomer layer and the backing metal layer being bonded, for example, by glue.
In general, the structure of the materials used in armor plating is such that they are difficult to glue and are often held on their support, in particular if made of aluminum or stainless steel or of composite materials, solely by a suction effect.
The object of the present invention is to remedy this drawback and to enable panels to be made which withstand intensive firing at very short time intervals.